For example, Patent Literature 1 describes a known switch device in which an operation unit and a switch unit operated by the operation unit are structured to be separable.
A conventional switch device 1 described in Patent Literature 1 is depicted in FIGS. 12 to 14.
A switch device 100 is provided with an operation unit 110 and a switch unit 120 which are structured mutually attachable and detachable. The operation unit 110 transmits a pushing operating force, which is applied from the outside, to the switch unit 120. The switch unit 120 receives the operating force from the operation unit 110 and opens/closes a plurality of opening/closing contact portions on the basis of the operating force.
The operation unit 110 is provided with an operation unit main body 111 and a pushbutton 113. The pushbutton 113 has a substantially round columnar shape, and the upper end surface of the pushbutton 113 receives the operating force from the outside in the axial direction. A protrusion 114 having a round columnar shape is provided in a protruding condition at the side surface on the lower end side of the pushbutton 113. Two guide grooves 112 having a substantially inverted L-shape are provided facing each other on the lower side of the side surface of the operation unit main body 111 for allowing the operation unit main body 111 to be rotated and fitted into the switch unit 120.
The pushbutton 113 of the operation unit 110 is supported by the operation unit main body 111 such that the pushbutton can move in the axial direction and cannot rotate in the rotation direction. As depicted in FIG. 14, a lock pin 116 which is caused by the urging force of a spring 115 to protrude from the inner wall of the operation unit main body 111 is provided at the operation unit main body 111, and a locking protrusion 117 which is to be engaged with the lock pin is provided in a protruding condition at the side surface of the pushbutton 113. As a result, when the upper surface of the pushbutton 113 is pushed down along a central axial line X by an operating force equal to or greater than a predetermined value, the lock pin 116 of the main body 111 is pushed in by the locking protrusion 117 against the urging force of the spring 115, and the pushbutton 113 moves downward to release the engagement of the locking protrusion 117 and the lock pin 116. When the locking protrusion 117 rides over the lock pin 116, the lock pin 116 protrudes and engages with the locking protrusion 117 again, and the pushbutton 113 is locked at a pushing position shown by a dot line (FIG. 14).
The switch unit 120 is provided with a partition wall 123 partitioning the inner space of a switch unit main body 121 in the horizontal direction, and a through hole 124 passing through along the central axial line X is provided in the central portion of the partition wall. Two engagement protrusions 122 to be engaged with the guide groove 112 of the operation unit 110 are integrally formed on the inner wall of the switch unit main body 121 above the partition wall 123.
A contact shaft 125 is inserted into the through hole 124 such that the contact shaft can move in the direction of the central axial line X, but cannot rotate about the central axial line X. A tubular pushbutton receptacle 126 into which the lower end portion of the pushbutton 113 is to be inserted from above is provided at the upper end of the contact shaft 125. A helical cut-out guide 127 which extends downward, while turning about the central axial line X, as shown in the figure, is provided in the circumferential side surface of the pushbutton receptacle 126 in order to engage with the protrusion 114 of the pushbutton 113.
An opening-closing contact mechanism 130 is accommodated in a space below the partition wall 123 in the switch unit main body 121. The opening-closing contact mechanism 130 is provided with a pair of fixed contactor pieces 132, each movable contactor piece being provided with a fixed contact 133, and a movable bridging piece 134 provided with a pair of movable contacts 135 at both ends. A distal end of the contact shaft 125 is joined to the central portion of the movable bridging piece 134, and a contact spring 131 that urges the movable bridging piece 134 in the direction of separating from the fixed contactor pieces 132 is attached to the contact shaft 125 between the movable bridging piece 134 and the partition wall 123. An external connection terminal piece 136 is drawn out to the outside of the main body 121 from each of the fixed contactor pieces 132. The fixed contact 133 of the fixed contactor piece 132 and the movable contact 135 of the movable bridging piece 134 are provided facing each other to enable contact and separation thereof.
The operation unit 110 is mounted on a panel (not shown in the figure).
In a state in which the switch unit 120 is separated from the operation unit 110, as depicted in FIG. 12, the movable bridging piece 134 is pulled apart from the fixed contactor pieces 132 by the contact spring 131, so that the contact shaft 125 moves downward, and the movable contacts 135 and the fixed contacts 133 are in a state (switch-off) separated from each other.
When the switch unit 120 is to be joined to the operation unit 110 from this state, initially, the switch unit 120 is fitted from below into the operation unit 110 so that the engagement protrusion 122 of the switch unit 120 is inserted into an inlet port of the guide groove 112 of the operation unit 110 and the protrusion 114 is inserted into an inlet port of the cut-out guide 127 of the switch unit.
Then, the switch unit main body 121 is turned in the direction of an arrow R (to the right) about the central axial line X. Since the pushbutton 113 is arranged to be incapable of rotating with respect to the operation unit main body 111, when the switch unit main body 121 is turned in the direction of arrow R, the protrusion 114 moves inside the helical cut-out guide 127. As a result, the protrusion 114 moves the pushbutton receptacle 126 upward, and following this movement, the movable contact 135 also moves upward, but when the switch unit main body 121 is stopped from turning, the movable contact 135 becomes a state (switch-on) contacting the fixed contact 133 (see FIG. 13(a)). The switch unit 120 is thus joined and fixed to the operation unit 110.
To detach the switch unit 120 from the operation unit 110, a procedure reversed to the procedure used to attach the switch unit 120 to the operation unit 110 is implemented. Thus, in a state in which the switch unit 120 depicted in FIG. 13(a) is attached to the operation unit 110, the switch unit 120 is turned in the direction of arrow L (to the left) about the central axial line X, the units are disconnected, and the switch unit 120 is detached from the operation unit 110 by further pulling downward (see FIG. 12). In this state, the movable contacts 135 and the fixed contacts 133 are urged by the contact spring 131 in the separation direction and separated from each other, and the open (switch-off) state is maintained.
With the switch device 100 having such an arrangement, in a standby state, the movable contacts 135 and the fixed contacts 133 are closed at all times and the switch-on state is maintained, as depicted in FIG. 13(a).
When the pushbutton 113 of the operation unit 110 is pushed down in this state, the movable bridging piece 134, which is linked to the pushbutton through the pushbutton receptacle 126 and the contact shaft 125, is lowered. Therefore, the movable contacts 135 are separated from the fixed contacts 133 and become the switch-off state (see FIG. 13(b)). As a result, when the switch device is used as an emergency switch, a stop command can be applied to the control object. In this case, since the pushbutton 113 is locked by the lock pin 116 at a position in which the locking protrusion 117 rides over the lock pin 116 at the pushing operation position shown by a dot line in FIG. 14, the pushbutton is held at the pushing operation position and maintained in the OFF state in which the movable contacts 135 are separated from the fixed contacts 133.
When an accident occurs such that the switch unit 120 joined to the operation unit 110 is detached from the operation unit 110, the movable contacts 135 of the switch unit 120 are urged by the return spring 131 in the separation direction and automatically separated from the fixed contacts 133 that have been in a closed state at all times, becoming a switch-off state (the state identical to the operation state). Therefore, when the switch device is used as an emergency stop switch, an accident causing the switch unit 120 to detach from the operation unit 110 results in a switch-off state. As a result, a stop command is issued to the control object and safety of the control object can be maintained.
Patent Literature 1: Japanese Patent Application Publication No. 2004-103363